Monitoring part-to-part gap and laser power effects in remote laser welding of 1050 aluminum busbar-to-terminal connections via optical microphone sensing

Advancements in membrane-free optical microphones have expanded their ability to detect acoustic signals up to tens of MHz, offering new possibilities for in-process monitoring of laser welding. Contributing to this growing field, this paper investigated part-to-part gap and laser power effects on weld events via optical microphone sensing. The study focused on remote laser welding of 1050 aluminum, representative of busbar-to-terminal connections. Acoustic emissions were collected and analyzed in the frequency domain using power spectral density calculations, identifying sound power as a critical signal feature. The findings reveal a strong correlation between the acoustic signals and the weld events, namely, lack of fusion, lack of connection, sound connection, and piercing. Notably, the adopted optical microphone effectively distinguished the transition from a blind to a passing-through keyhole, triggered by laser piercing, as well as the transition from lack of fusion to sound connections through lack of connection. These results demonstrated the potential of optical microphones for real-time, in-process monitoring of laser welding processes, thereby laying the groundwork for enhanced quality control of laser weldments.